The sites and mechanism of action of antimicrobial agents isolated from marine plants (primarily Rhodophyta and Phaeophyta) and animals (primarily Porifera and Holothuroidea) will be studied. The effects of the marine compounds on synthetic processes, respiration and permeability will be determined in whole cells of bacteria and fungi will be determined. The action of the antimicrobial agents or specific enzymes or enzyme systems from eukaryotes and prokaryotes will be studied in extracts of appropriate species.